As he wrapped up his three-nation Asia visit, top US diplomat John Kerry warned that the future stability of the region would depend on how well, and how soon, Asean members and China agreed on rules to manage tensions in the South China Sea.

"The longer the process takes, the longer tensions will simmer, and the greater the chance of a miscalculation by somebody that could trigger a conflict," he said.

"That is in nobody's interests," he told a joint press conference yesterday with Indonesian Foreign Minister Marty Natalegawa, who has regularly stressed the need for such guidelines.

On Sunday, he and Asean secretary-general Le Luong Minh also emphasised the urgency of concluding a Code of Conduct early, as well as the importance of respecting international law and exercising self-restraint.

Kerry told Minh that President Barack Obama was looking forward to the second Asean-US summit in Myanmar later this year. Obama will also visit Malaysia and the Philippines in April.

It is unclear whether Kerry's remarks will expedite the process of drafting a code, but they appear aimed at reassuring the region that the United States backs the need for China to adopt a rule of law-based approach towards the South China Sea - a point Kerry made in Beijing last week.

Dr Marty told reporters later that progress on the Asean-China code had been good thus far.

"China is very much presenting itself as a part of the solution," he said.

Details of their conversation were not immediately available, but the move appeared to douse talk of a snub, as Dr Yudhoyono had been scheduled to receive the US diplomat yesterday. But the President left town by train on Sunday to visit victims of Mount Kelud's volcanic eruption, 700km east of the capital.

Dr Yudhoyono's trip came as news reports broke of Australian intelligence offering the US National Security Agency information from surveillance of Indonesian officials talking to US lawyers about a trade dispute.

Dr Marty noted that the US, unlike Australia, was undertaking a comprehensive review of its intelligence-gathering practices, while Kerry said Washington was taking the matter very seriously.

Dr Yudhoyono has also pushed for the Code of Conduct to be concluded early. Asean and China started talks on the code in Suzhou last September, after years of resistance from Beijing.

But officials expect progress to be gradual, citing how Chinese officials warned against rushing to draw up these rules of behaviour.

Dr Makmur Keliat of the University of Indonesia said that while a code of conduct is important in helping to de-escalate regional tensions, countries also had to be prepared that it might not work in the event of a crisis.

Kerry's efforts to reach out to Asean come as regional concern grows over China's recent unilateral moves to assert its maritime claims in the South China Sea, as well as the East China Sea.

US Assistant Secretary of State Daniel Russel earlier this month urged China to clarify its South China Sea claims which, he said, had no basis in international law.